1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/mount.h> 3 #include <linux/pseudo_fs.h> 4 #include <linux/file.h> 5 #include <linux/fs.h> 6 #include <linux/proc_fs.h> 7 #include <linux/proc_ns.h> 8 #include <linux/magic.h> 9 #include <linux/ktime.h> 10 #include <linux/seq_file.h> 11 #include <linux/user_namespace.h> 12 #include <linux/nsfs.h> 13 #include <linux/uaccess.h> 14 15 #include "internal.h" 16 17 static struct vfsmount *nsfs_mnt; 18 19 static long ns_ioctl(struct file *filp, unsigned int ioctl, 20 unsigned long arg); 21 static const struct file_operations ns_file_operations = { 22 .llseek = no_llseek, 23 .unlocked_ioctl = ns_ioctl, 24 .compat_ioctl = compat_ptr_ioctl, 25 }; 26 27 static char *ns_dname(struct dentry *dentry, char *buffer, int buflen) 28 { 29 struct inode *inode = d_inode(dentry); 30 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 31 32 return dynamic_dname(buffer, buflen, "%s:[%lu]", 33 ns_ops->name, inode->i_ino); 34 } 35 36 static void ns_prune_dentry(struct dentry *dentry) 37 { 38 struct inode *inode = d_inode(dentry); 39 if (inode) { 40 struct ns_common *ns = inode->i_private; 41 atomic_long_set(&ns->stashed, 0); 42 } 43 } 44 45 const struct dentry_operations ns_dentry_operations = 46 { 47 .d_prune = ns_prune_dentry, 48 .d_delete = always_delete_dentry, 49 .d_dname = ns_dname, 50 }; 51 52 static void nsfs_evict(struct inode *inode) 53 { 54 struct ns_common *ns = inode->i_private; 55 clear_inode(inode); 56 ns->ops->put(ns); 57 } 58 59 static int __ns_get_path(struct path *path, struct ns_common *ns) 60 { 61 struct vfsmount *mnt = nsfs_mnt; 62 struct dentry *dentry; 63 struct inode *inode; 64 unsigned long d; 65 66 rcu_read_lock(); 67 d = atomic_long_read(&ns->stashed); 68 if (!d) 69 goto slow; 70 dentry = (struct dentry *)d; 71 if (!lockref_get_not_dead(&dentry->d_lockref)) 72 goto slow; 73 rcu_read_unlock(); 74 ns->ops->put(ns); 75 got_it: 76 path->mnt = mntget(mnt); 77 path->dentry = dentry; 78 return 0; 79 slow: 80 rcu_read_unlock(); 81 inode = new_inode_pseudo(mnt->mnt_sb); 82 if (!inode) { 83 ns->ops->put(ns); 84 return -ENOMEM; 85 } 86 inode->i_ino = ns->inum; 87 simple_inode_init_ts(inode); 88 inode->i_flags |= S_IMMUTABLE; 89 inode->i_mode = S_IFREG | S_IRUGO; 90 inode->i_fop = &ns_file_operations; 91 inode->i_private = ns; 92 93 dentry = d_make_root(inode); /* not the normal use, but... */ 94 if (!dentry) 95 return -ENOMEM; 96 dentry->d_fsdata = (void *)ns->ops; 97 d = atomic_long_cmpxchg(&ns->stashed, 0, (unsigned long)dentry); 98 if (d) { 99 d_delete(dentry); /* make sure ->d_prune() does nothing */ 100 dput(dentry); 101 cpu_relax(); 102 return -EAGAIN; 103 } 104 goto got_it; 105 } 106 107 int ns_get_path_cb(struct path *path, ns_get_path_helper_t *ns_get_cb, 108 void *private_data) 109 { 110 int ret; 111 112 do { 113 struct ns_common *ns = ns_get_cb(private_data); 114 if (!ns) 115 return -ENOENT; 116 ret = __ns_get_path(path, ns); 117 } while (ret == -EAGAIN); 118 119 return ret; 120 } 121 122 struct ns_get_path_task_args { 123 const struct proc_ns_operations *ns_ops; 124 struct task_struct *task; 125 }; 126 127 static struct ns_common *ns_get_path_task(void *private_data) 128 { 129 struct ns_get_path_task_args *args = private_data; 130 131 return args->ns_ops->get(args->task); 132 } 133 134 int ns_get_path(struct path *path, struct task_struct *task, 135 const struct proc_ns_operations *ns_ops) 136 { 137 struct ns_get_path_task_args args = { 138 .ns_ops = ns_ops, 139 .task = task, 140 }; 141 142 return ns_get_path_cb(path, ns_get_path_task, &args); 143 } 144 145 int open_related_ns(struct ns_common *ns, 146 struct ns_common *(*get_ns)(struct ns_common *ns)) 147 { 148 struct path path = {}; 149 struct file *f; 150 int err; 151 int fd; 152 153 fd = get_unused_fd_flags(O_CLOEXEC); 154 if (fd < 0) 155 return fd; 156 157 do { 158 struct ns_common *relative; 159 160 relative = get_ns(ns); 161 if (IS_ERR(relative)) { 162 put_unused_fd(fd); 163 return PTR_ERR(relative); 164 } 165 166 err = __ns_get_path(&path, relative); 167 } while (err == -EAGAIN); 168 169 if (err) { 170 put_unused_fd(fd); 171 return err; 172 } 173 174 f = dentry_open(&path, O_RDONLY, current_cred()); 175 path_put(&path); 176 if (IS_ERR(f)) { 177 put_unused_fd(fd); 178 fd = PTR_ERR(f); 179 } else 180 fd_install(fd, f); 181 182 return fd; 183 } 184 EXPORT_SYMBOL_GPL(open_related_ns); 185 186 static long ns_ioctl(struct file *filp, unsigned int ioctl, 187 unsigned long arg) 188 { 189 struct user_namespace *user_ns; 190 struct ns_common *ns = get_proc_ns(file_inode(filp)); 191 uid_t __user *argp; 192 uid_t uid; 193 194 switch (ioctl) { 195 case NS_GET_USERNS: 196 return open_related_ns(ns, ns_get_owner); 197 case NS_GET_PARENT: 198 if (!ns->ops->get_parent) 199 return -EINVAL; 200 return open_related_ns(ns, ns->ops->get_parent); 201 case NS_GET_NSTYPE: 202 return ns->ops->type; 203 case NS_GET_OWNER_UID: 204 if (ns->ops->type != CLONE_NEWUSER) 205 return -EINVAL; 206 user_ns = container_of(ns, struct user_namespace, ns); 207 argp = (uid_t __user *) arg; 208 uid = from_kuid_munged(current_user_ns(), user_ns->owner); 209 return put_user(uid, argp); 210 default: 211 return -ENOTTY; 212 } 213 } 214 215 int ns_get_name(char *buf, size_t size, struct task_struct *task, 216 const struct proc_ns_operations *ns_ops) 217 { 218 struct ns_common *ns; 219 int res = -ENOENT; 220 const char *name; 221 ns = ns_ops->get(task); 222 if (ns) { 223 name = ns_ops->real_ns_name ? : ns_ops->name; 224 res = snprintf(buf, size, "%s:[%u]", name, ns->inum); 225 ns_ops->put(ns); 226 } 227 return res; 228 } 229 230 bool proc_ns_file(const struct file *file) 231 { 232 return file->f_op == &ns_file_operations; 233 } 234 235 /** 236 * ns_match() - Returns true if current namespace matches dev/ino provided. 237 * @ns: current namespace 238 * @dev: dev_t from nsfs that will be matched against current nsfs 239 * @ino: ino_t from nsfs that will be matched against current nsfs 240 * 241 * Return: true if dev and ino matches the current nsfs. 242 */ 243 bool ns_match(const struct ns_common *ns, dev_t dev, ino_t ino) 244 { 245 return (ns->inum == ino) && (nsfs_mnt->mnt_sb->s_dev == dev); 246 } 247 248 249 static int nsfs_show_path(struct seq_file *seq, struct dentry *dentry) 250 { 251 struct inode *inode = d_inode(dentry); 252 const struct proc_ns_operations *ns_ops = dentry->d_fsdata; 253 254 seq_printf(seq, "%s:[%lu]", ns_ops->name, inode->i_ino); 255 return 0; 256 } 257 258 static const struct super_operations nsfs_ops = { 259 .statfs = simple_statfs, 260 .evict_inode = nsfs_evict, 261 .show_path = nsfs_show_path, 262 }; 263 264 static int nsfs_init_fs_context(struct fs_context *fc) 265 { 266 struct pseudo_fs_context *ctx = init_pseudo(fc, NSFS_MAGIC); 267 if (!ctx) 268 return -ENOMEM; 269 ctx->ops = &nsfs_ops; 270 ctx->dops = &ns_dentry_operations; 271 return 0; 272 } 273 274 static struct file_system_type nsfs = { 275 .name = "nsfs", 276 .init_fs_context = nsfs_init_fs_context, 277 .kill_sb = kill_anon_super, 278 }; 279 280 void __init nsfs_init(void) 281 { 282 nsfs_mnt = kern_mount(&nsfs); 283 if (IS_ERR(nsfs_mnt)) 284 panic("can't set nsfs up\n"); 285 nsfs_mnt->mnt_sb->s_flags &= ~SB_NOUSER; 286 } 287